1. Field of the Invention
The present invention relates to processes for reducing the relative content of olefins having a terminal CF2 group in a mixture thereof with hydrocarbons and/or halohydrocarbons by using selective removal agents.
2. Description of Related Art
Halogenated compounds, especially fluorinated compounds, such as fluorocarbons and hydrofluorocarbons, have been widely used as refrigerants, solvents, cleaning agents, foam blowing agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishing agents, sterilants and power cycle working fluids, et al. Purification is an important step in manufacturing these compounds. Distillation is typically used to separate desired products from impurities; however, purification becomes difficult or impossible when the desired compound has a boiling point close to that of one or more of the impurities.
For example, 1,2,3,3,3-pentafluoropropene (HFC-1225ye), having zero ozone depletion and low global warming potentials, has been identified as a potential refrigerant. However, the manufacture of 1,2,3,3,3-pentafluoropropene can also result in the formation of an isomeric contaminant, 1,1,3,3,3-pentafluoropropene (HFC-1225zc). As Singh et al. indicate in US Patent Application 2004/0119047, 1,1,3,3,3-pentafluoropropene exhibits toxicity. However, the boiling point of 1,2,3,3,3-pentafluoropropene is −19.9° C. and the boiling point of 1,1,3,3,3-pentafluoropropene is −21.8° C. Thus, removing 1,1,3,3,3-pentafluoropropene from a mixture containing 1,2,3,3,3-pentafluoropropene and 1,1,3,3,3-pentafluoropropene by distillation is difficult.
There is a need to develop other processes for reducing the relative content of compounds such as 1,1,3,3,3-pentafluoropropene which have a terminal CF2 group.